Diagenetic Evolution and Its Impact on Reservoir Quality of Tight Sandstones: A Case Study of the Triassic Chang-7 Member, Ordos Basin, Northwest China

Wei Yu, Feng Wang (), Xianyang Liu (), Jingchun Tian, Tian Yang, Zhaocai Ren and Li Gong
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Wei Yu: Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
Feng Wang: Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
Xianyang Liu: Research Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi’an 710018, China
Jingchun Tian: Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
Tian Yang: Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
Zhaocai Ren: Research Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi’an 710018, China
Li Gong: Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China

Energies, 2023, vol. 16, issue 5, 1-20

Abstract: The Upper Triassic Chang-7 Member of the Ordos Basin contains typical tight sandstone reservoirs. Reservoir quality is affected by diagenesis, which is a critical factor in tight oil exploration. In this study, the Chang-7 Member tight sandstones were studied by a variety of experimental methods, including thin sections, scanning electron microscopy (SEM), and X-ray diffraction (XRD), to determine the reservoir characteristics and diagenesis and discuss their influences on the reservoir quality. The Chang-7 Member sandstones are mainly lithic arkose and feldspathic litharenite with an average porosity and permeability of 7.17% and 0.13 mD, respectively. The pore type is mainly primary intergranular pores, and the secondary pores are feldspar dissolved pores, which are relatively developed, with pore radii of 2–20 µm. Diagenesis of Chang-7 Member tight reservoirs mainly includes compaction, quartz cementation, carbonate cementation, clay mineral cementation, and dissolution. The diagenetic stage develops into Mesodiagenesis A. The average porosity loss from compaction and cementation of sandstone in the Chang-7 Member is 15.93% and 18.67%, respectively. With the increase in burial depth, the porosity and permeability of the reservoir gradually decrease. In mesodiagenesis, the authigenic illite and carbonate cementation compacts the reservoir. The acid fluid carried by the two stages of oil and gas filling during diagenesis dissolved feldspar and carbonate cement, which plays a certain role in transforming the tight reservoir.

Keywords: tight sandstone; reservoir quality; diagenesis; Chang-7 Member; Ordos Basin (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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